Effects of Coal Mining Subsided Water Area on Temperature Change in Huaibei Coal Mine

[Objective] The study aimed to discuss the effects of coal mining subsided water area on temperature change in Huaibei coal mine. [Method] Based on the data of monthly temperature from 1957 to 2007 recorded by Suixi （coal mining subsided water area） and Fuyang stations （control）, the effects of coal mining subsided water area on temperature change in Huaibei coal mine were discussed using linear trend estimation and comparative analysis methods. [Result] Spring, autumn, winter and annual average temperatures of coal mining subsided water area （Suixi） were increased in the last 51 years, and the increase of winter temperature was mostly significant with a tendency rate of 0.49 ℃/10 a. Meanwhile, annual temperature range of coal mining subsided water area was decreased from 1957 to 2007. Temperatures of Suixi in four seasons were lower than those of Fuyang from the 1960s to 1990s, and temperatures of coal mining subsided water area （Suixi） were higher than those of Fuyang in spring, autumn and winter but lower than those of Fuyang in summer from 2000 to 2007. [ Result] Coal mining subsided water area had certain effects on temperature change of Huaibei coal mine.

Analysis of Characteristic and Causes of a Strong Cooling Process in China in the Early Winter of 2020/2021

The characteristics and causes of a drop in temperature during a cold wave process in the early winter of 2020/2021 were analyzed.The results show that the air temperature at 700-600 hPa over China was firstly and mostly influenced by the cold wave process,and then the cold air gradually extended to the lower layer,causing the most severe cooling in North China and its nearby areas.During the cold wave,the longitude of the upper-level jet over the Chinese mainland was larger;the Ural blocking high and the East Asian trough were stronger,so that the geopotential height gradient between the two was also significantly larger;the meridional air flow was abnormally strong,which was conducive to the southward transport of cold air from the middle and high latitudes.Results of the diagnostic analysis further show that the outbreak of the cold wave and the negative temperature tendency anomaly in the key area were mainly caused by the meridional temperature horizontal advection anomaly,while the temperature rise accompanied by abnormal air subsidence compensated for the abnormal decrease in temperature,which was conducive to the gradual rise of temperature in the key area.

Understanding the physical processes in the evolution of a cold air outbreak over China in late November 2022 from a Lagrangian perspective

From 26 November to 1 December 2022,intense cold air masses swept across China from northwest to south,resulting in a nationwide cold air outbreak(CAO)case characterised by drastic and sudden temperature drops with rain,snow and strong winds.The physical processes that dominate the intensification of the cold air masses during this CAO event remain unclear.In this study,the evolution of the CAO case,which is indicated by the dry static energy(DSE),is investigated using a novel approach in the framework of Lagrangian backtracking.The dominant processes can be identified by decomposing the DSE change into four diabatic heating terms due to shortwave radiation,longwave radiation,latent heat and turbulent processes.Overall,in this case,most of the cold air parcels originated from the east of Novaya Zemlya and crossed Central Siberia before reaching China.Thus,these air parcels mainly manifested on the northwest‒southeast path.The duration of the cold air intensification differed between subregions.The cold air parcels experienced long cooling periods(approximately 9 d)before reaching northern China(i.e.Northwest,North and Northeast China),whilst the southern parts(i.e.Central,East and South China)underwent relatively short cooling periods(6-8 d).Accordingly,the cold air affecting northern China is more intense than that affecting the southern parts,especially for East and South China.For all six subregions,longwave radiative cooling is identified as the dominant contributor to the cold air intensification,and the latent heat processes as the secondary contributor.The weakening of cold air parcels as they approach and pass over these regions is driven by turbulent processes and shortwave heating.Central Siberia and Lake Baikal are identified as key areas for the intensification of cold air passing over both regions.In addition,air parcels affecting Northwest China are intensely cooled as they pass over the Junggar Basin,while the North China Plain is a key area for cooling air parcels reaching Central,East and South China.From a Lagrangian perspective,these findings provide insights into the physical processes driving the behaviour of cold air parcels,which would help understand the mechanisms involved in the past changes and future projections in CAOs.